Conventional setting of a parameter value using an analog volume has a problem in which, it has a limitation in resolution due to its limited operation range, and is not suitable for an operation to increase or decrease a parameter value one by one. The analog volume is an operator showing an absolute value, and when a function is assignable to the analog volume, an operator position and an actual value do not match each other in some cases, so that operability is not preferable.
These problems are solved by use of an incremental rotary encoder that starts from an arbitrary starting point and changes a parameter value according to a rotation amount. On the other hand, when a parameter value changes significantly from, for example, a minimum value to a maximum value, the operator needs to be moved (a dial or knob needs to be rotated) many times, and this cannot make a quick change in parameter value in the same way that an operator using an analog volume does.
Patent Document 1 discloses a technology to change, in a rotary encoder, a movement amount of a cursor per unit time according to a rotation speed (the cursor quickly moves when the knob is quickly rotated, and the cursor slowly moves when the knob is slowly rotated).